Where can I find electronic data of state territorial waters at 3 nautical miles (or 9 nautical miles off of Texas, Puerto Rico, and the west coast of Florida)?

The Bureau of Ocean Energy Management (BOEM) manages and disseminates the Submerged Lands Act federal/state boundaries. Electronic data is here. Go to the links under “GIS Data / Shapefiles” to download data for a specific region. Note: the Gulf of Mexico dataset is in the sub-link, Gulf of Mexico Geographic Mapping Data.

The maritime limits are created using “envelope of arcs,” a method by which one rolls a virtual circle along the charted low water line and selects salient points. These salient points are called "contributing baseline points." Arcs generated from these baseline points are blended together to form a continuous limit line or envelope of arcs.

The U.S. Baseline Committee reviews and approves the limits of all maritime zones on NOAA charts. It gains interagency consensus on the proper location of the baseline, using the provisions of the 1958 Convention on the Territorial Sea and the Contiguous Zone, to ensure that the seaward extents of U.S. maritime zones do not exceed the breadth permitted by international law. Current members of the Committee include the Departments of State (Chair), Commerce (NOAA), Justice, Interior (BOEM), and Homeland Security (Coast Guard), among others.

What initiates updates to the digital U.S. maritime limits and boundaries?

The primary triggers for updates include accretion or erosion of the charted low water line by approximately 500 meters or more, or changes to low tide elevations (i.e., rocks awash) as a result of new hydrographic survey information. The Office of Coast Survey and the Baseline Committee will investigate these changes for new edition chart. There are approximately 12 new editions issued each month, and a small number of these charts depict features that impact the U.S. baseline or maritime limits. The Baseline Committee, which meets four to six times per year, reviews and approved all proposed revisions.

Another trigger for change may be the U.S. ratification of a new treaty with a neighboring coastal State. Some areas for future change include the U.S. waters adjacent to Canada, the Bahamas, Kiribati, Tonga, and the Federated States of Micronesia, to name a few.

The WMS can be used in various desktop GIS software as well as web mapping applications. The WMS link leads to the GetCapabilities page, which provides easy-to-read, detailed information about the data as well as the necessary link to load the data into a GIS or web mapping application. Open Geospatial Consortium (OGC) provides more information about web mapping services.

For users who prefer to work within the ESRI software environment, we provide an ESRI REST (Representational State Transfer) service. This service can be used in ESRI’s ArcGIS Desktop software or in ESRI’s free ArcGIS Explorer Desktop. It can also be added as a layer in web mapping services, such as ArcGIS Online.

What information is provided with the dataset?

The dataset includes specific information about each maritime boundary segment. Attributes for the data are:

Boundary ID: a unique identifier of the boundary segment
Region Name: region in which the boundary is located
Type of Feature: features can either be a land boundary (between the U.S. and Canada), a maritime limit, or a maritime boundary between the U.S. and an adjacent or opposite country.
Publication Date: date the digital boundary was published online
Approval Date: date the U.S. Baseline Committee approved the updates
Legal Authority: treaty, agreement, or proclamation granting the government authority to establish the limit or boundary.
Agency of Responsibility: federal agency responsible for maintaining the digital data
Note: additional notes about the limit/boundary
Supplemental Information Document: ink to metadata about the specific boundary segment. The document supplements the parent metadata record.
Unilateral Claim: some maritime boundary claims have not been agreed upon by all parties. These boundaries are designated as unilateral claims.
Description: specific category of maritime limit/boundary.

Why is the digital product different from the product printed on the chart?

Because of a difference in the chart printing schedule and the digital data update schedule, the digital data and the paper charts might not always be identical. In the event that the digital product and the paper charts differ, the maritime limits and boundaries on the paper charts take precedence.

How can I access the three nautical mile line that is printed on NOAA nautical charts?

We find that most people who seek this line are actually looking for the Submerged Lands Act federal/state boundary provided by BOEM (see FAQ #1). For those seeking the ambulatory three nautical mile territorial sea limit, we recommend that you use the seamless raster nautical chart service provided by the Office of Coast Survey.